This study asks what factors are involved in maintaining cell polarity during a series of unequal cell divisions in embryos of the roundworm C. elegans. Mutant embryos with prolonged cell cycles lose cell polarity and undergo abnormally equal cell divisions. I will reexamine cell division phenotypes in slow-cleaving mutants. Several mutant strains will be subjected to RNA-mediated interference (RNAi) to find out what additional genetic insults will modify their phenotype. Genes that affect kinetics of either cell cycle or polarity are expected to be recovered in this screen, and the RNiI method will allow genes of interest to be rapidly isolated for further analysis. At least two genes already known to affect both early cell cycle timing and later differentiation will also be cloned and functionally studied. This project aims to shed light on basic mechanisms of animal cells, in particular those modulating rates of DNA replication and cytoplasmic reorganization.